One well known torch, which has been used to fabricate lightguide preforms is described in detail in U.S. Pat. No. 4,401,267 and is assigned to the instant assignee. That torch is comprised of an arcuate plate captured between first and second arcuate outer members, each outer member having a cavity therein which opens toward the plate. The plate has a plurality of uniformly spaced grooves on each major surface thereof, arranged in an interleaved relationship, the grooves extending from the respective cavities in the outer members to an outer edge of the plate to form a plurality of gas outlets.
A first gas (e.g., oxygen) exits from alternate grooves at the outer edge while a second gas (e.g., hydrogen) exits from the remaining grooves. This torch has been found to be most effective in fabricating lightguide preforms. However, the arcuate shape and the radial grooves result in a flame build-up in the vicinity of the lightguide preform tube which provides a relative wide heat zone. Such a wide heat zone is desirable for fabricating lightguide preforms but presents problems when only a narrow portion of a tube or other article is to be heated. In some instances it is necessary to heat relatively narrow areas of the glass tube to selectively collapse portions of the tube.
Accordingly, there is a need for a torch which can provide a narrow heat zone and is relatively inexpensive and can be readily assembled or disassembled to repair.